The present invention relates to vapor deposition and, more particularly, to physical vapor deposition of ceramic materials to form coatings on substrates.
Ceramic coatings are applied to gas turbine engine hardware, such as turbine blades and vanes, to provide thermal protection against the high temperatures of the turbine engine. For example, so called thermal barrier coatings are applied to gas turbine engine blade and vane components by first depositing a bondcoat on the component followed by depositing a ceramic layer on the bondcoat by electron beam physical vapor deposition. In the electron beam physical vapor deposition of the ceramic layer, a source of the ceramic material, such as yttria stabilized zirconia, is heated by impinging an electron beam thereon to evaporate the ceramic material for deposition on the components, which are positioned in the ceramic vapor cloud to this end.
The electron beam physical vapor deposition of the ceramic layer on the turbine components is conducted in a stainless steel or other coating box or enclosure, which may be water cooled. It has been discovered by applicants that during the course of coating with the evaporated ceramic material, the ceramic coating material inadvertently collects on the inside walls of the relatively cool coating box or enclosure in addition to depositing on the components to be coated. The collected ceramic material has been found to act as thermal insulation on the inside enclosure walls to an extent that excess heat can build up in the coating box or enclosure exceeding the preselected desired coating temperature for the particular components to be coated, resulting in defective or unacceptable coated components.
It is an object of the present invention to provide method and apparatus that overcome the aforementioned problem and provide control of coating temperature during vapor deposition in a coating box or enclosure.
The present invention provides control of coating temperature during vapor deposition in a coating box or enclosure by means of a heat release lid or cover on the coating enclosure and movable in response to temperature in the coating enclosure so as to release excess heat from a heat vent opening of the enclosure to maintain coating temperature within an appropriate range.
In an illustrative embodiment of the present invention, a water cooled or non-cooled metal (e.g. water cooled copper or non-cooled stainless steel) coating enclosure includes a heat release cover movable relative to a heat vent opening of the enclosure. An actuator is connected to the heat release cover for raising away from the opening to discharge or vent excess heat in response to temperature inside the enclosure exceeding a predetermined value to maintain coating temperature within an appropriate range. Temperature in the coating enclosure is sensed by a thermocouple or other temperature sensing device and provides a temperature feedback signal to an automatic actuator or to a temperature gage monitored by a coating operator who raises or lowers the lid in response to sensed temperature in the coating enclosure.
The above objects and advantages of the present invention will become more readily apparent from the following detailed description taken with the following drawings.